The production of reformulated gasoline satisfying new environmental regulations requires, in particular, a reduction in the concentration of olefins and/or aromatics (especially benzene), also sulphur, and particularly mercaptans.
As an example, the presence of diolefins in catalytic cracking gasolines risks the formation of gums which mean that such raw gasolines are difficult to use as a fuel.
The diolefins must therefore be eliminated before etherification.
We have already developed a process for selective hydrogenation of a catalytic cracking gasoline which eliminates diolefins and which consists of bringing the feed into contact with a catalyst containing 0.1-1% of palladium deposited on a support. Such a process is described in European patent EP-A-0 685 552.
Further, oxidizing sweetening is a reaction which is well suited to ensuring that malodorous compounds in catalytic cracking gasolines do not pass into the gasoline pool.
A sweetening process has been described in EP-A-0 638 628 which consists of bringing the cut to be treated into contact, in the presence of air, with a catalyst comprising an alkaline aluminosilicate, activated charcoal and a metal chelate.
Unfortunately, when gasolines which contain a large quantity of mercaptans (at least 120 ppm) are treated, in order to obtain a mercaptan level which satisfies the regulations, low space velocities or large quantities of catalyst must be used, or a plurality of sweetening reactors must be used. These constraints are highly problematic for the operator.